The present invention relates to a method and an apparatus for controlling a reduction ratio of a continuously variable transmission of an automotive vehicle.
A known continuously variable transmission has a V-belt running over a drive pulley and a driven pulley, each having a cylinder chamber and two conical discs. One conical disc of the drive pulley is secured to a drive shaft adapted to be driven by an engine, while one conical disc of the driven pulley is secured to a driven shaft. The other conical disc of the drive pulley is controllably movable in an axial direction of the drive shaft in response to the fluid pressure in the cylinder chamber thereof. Similarly, the other conical disc of the driven pulley is controllably movable in an axial direction of the driven shaft in response to the fluid pressure in the cylinder chamber thereof. For controlling the reduction ratio, a shift control value actuated by a shift motor, regulates fluid supply to and discharge from the cylinder chambers.